Use trait collection to resolve border colors

c974cbf changed the border colors to be of UIColor instead of CGColor. This allowed working with dark mode to switch the border colors automatically. However, in certain situation the system can't resolve the current trait collection (see https://stackoverflow.com/a/57177411/2525941). This commit resolves the colors with the current trait collection to ensure the right colors are selected. This matches with the behavior of how the background color is resolved (also in displayLayer:).

React/Views/RCTView.m

@@ -706,33 +706,43 @@ - (RCTCornerRadii)cornerRadii
   };
 }
 
-- (RCTBorderColors)borderColors
+- (RCTBorderColors)borderColorsWithTraitCollection:(UITraitCollection *)traitCollection
 {
   const BOOL isRTL = _reactLayoutDirection == UIUserInterfaceLayoutDirectionRightToLeft;
 
+  UIColor *directionAwareBorderLeftColor = nil;
+  UIColor *directionAwareBorderRightColor = nil;
+
   if ([[RCTI18nUtil sharedInstance] doLeftAndRightSwapInRTL]) {
     UIColor *borderStartColor = _borderStartColor ?: _borderLeftColor;
     UIColor *borderEndColor = _borderEndColor ?: _borderRightColor;
 
-    UIColor *directionAwareBorderLeftColor = isRTL ? borderEndColor : borderStartColor;
-    UIColor *directionAwareBorderRightColor = isRTL ? borderStartColor : borderEndColor;
-
-    return (RCTBorderColors){
-        (_borderTopColor ?: _borderColor).CGColor,
-        (directionAwareBorderLeftColor ?: _borderColor).CGColor,
-        (_borderBottomColor ?: _borderColor).CGColor,
-        (directionAwareBorderRightColor ?: _borderColor).CGColor,
-    };
+    directionAwareBorderLeftColor = isRTL ? borderEndColor : borderStartColor;
+    directionAwareBorderRightColor = isRTL ? borderStartColor : borderEndColor;
+  } else {
+    directionAwareBorderLeftColor = (isRTL ? _borderEndColor : _borderStartColor) ?: _borderLeftColor;
+    directionAwareBorderRightColor = (isRTL ? _borderStartColor : _borderEndColor) ?: _borderRightColor;
   }
 
-  UIColor *directionAwareBorderLeftColor = isRTL ? _borderEndColor : _borderStartColor;
-  UIColor *directionAwareBorderRightColor = isRTL ? _borderStartColor : _borderEndColor;
+  UIColor *borderColor = _borderColor;
+  UIColor *borderTopColor = _borderTopColor;
+  UIColor *borderBottomColor = _borderBottomColor;
+
+#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 130000
+  if (@available(iOS 13.0, *)) {
+    borderColor = [borderColor resolvedColorWithTraitCollection:self.traitCollection];
+    borderTopColor = [borderTopColor resolvedColorWithTraitCollection:self.traitCollection];
+    directionAwareBorderLeftColor = [directionAwareBorderLeftColor resolvedColorWithTraitCollection:self.traitCollection];
+    borderBottomColor = [borderBottomColor resolvedColorWithTraitCollection:self.traitCollection];
+    directionAwareBorderRightColor = [directionAwareBorderRightColor resolvedColorWithTraitCollection:self.traitCollection];
+  }
+#endif
 
   return (RCTBorderColors){
-    (_borderTopColor ?: _borderColor).CGColor,
-    (directionAwareBorderLeftColor ?: _borderLeftColor ?: _borderColor).CGColor,
-    (_borderBottomColor ?: _borderColor).CGColor,
-    (directionAwareBorderRightColor ?: _borderRightColor ?: _borderColor).CGColor,
+      (borderTopColor ?: borderColor).CGColor,
+      (directionAwareBorderLeftColor ?: borderColor).CGColor,
+      (borderBottomColor ?: borderColor).CGColor,
+      (directionAwareBorderRightColor ?: borderColor).CGColor,
   };
 }
 
@@ -758,7 +768,7 @@ - (void)displayLayer:(CALayer *)layer
 
   const RCTCornerRadii cornerRadii = [self cornerRadii];
   const UIEdgeInsets borderInsets = [self bordersAsInsets];
-  const RCTBorderColors borderColors = [self borderColors];
+  const RCTBorderColors borderColors = [self borderColorsWithTraitCollection:self.traitCollection];
 
   BOOL useIOSBorderRendering = RCTCornerRadiiAreEqual(cornerRadii) && RCTBorderInsetsAreEqual(borderInsets) &&
       RCTBorderColorsAreEqual(borderColors) && _borderStyle == RCTBorderStyleSolid &&